Trussed bridge structure



Sept. 11, 1956 J. N. LAYCOCK 2,762,069

TRUSSED BRIDGE STRUCTURE I Filed May 17, 1951 3 Sheets-Sheet 1 INVENTOR. JOHN N. LAYCOCK 2/12 rillaw i ATTORNEYS Sept. 11, 1956 J. N. LAYCOCK 2,762,069

TRUSSED BRIDGE STRUCTURE Filed May 17, 1951 5 sheets-sheet 2 Fig. 4

Fig. 6

42" 4o 42 4o 42' 40" 7 W v H, '1 'k -|y 1 Q- INVENTOR.

' JOHN N. LAYCOCK BY fmm 7W 21,225. *Mum ATTORNEYS Sept. 11, 1956 J, N. LAYCOCK 2,762,069

TRUSSED BRIDGE STRUCTURE Filed May 17, 1951 5 Sheets-Sheet s Fig. 7

INVENTOR.

JOH N N. LAYCOCK ATTORNEYS United States Patent 9 TRUSSED BRIDGE dTRUCTURE John N. Laycock, Derry, N. H.

Application May 17, 1951, Serial No. 226,823

8 Claims. (Cl. 141) The present invention relates to improvements in portable folding trussed craft units and, in particular, to improvements relating to the subject matter disclosed in my copending application Ser. No. 226,822, filed concurrently herewith, now Patent No. 2,669,960. Reference is made to said application for a complete discussion of the details of a trussed craft unit to which the improvements of the present invention may conveniently be applied.

The most important object of my invention is to provide conveniently operable and relatively inexpensive means for stiflening an assembly of several buoyant deck grids joined serially by hinges so that an assembly of such deck grids may be relatively rigidly held in position against articulation about the hinges when subject to load stresses of various kinds.

Another important object of the invention is to provide a plurality of hinged deck grids combined with stifiening means rendering the grids capable of being easily assembled into comparatively rigid structures useful as bridges, ramps, and the like.

These and other objects and features of the invention will be more readily understood and appreciated from the following detailed description of preferred embodiments thereof selected for purposes of illustration and shown in the accompanying drawings, in which:

Fig. l is a View in side elevation of a pair of deck grid sections illustrating the position of the pontoons in their collapsed state and the truss members parallel to the grid sections,

Fig. 2 is a view in side elevation of a deck grid assembly with inflated pontoons and lowered side trusses,

Fig. 3- is a view in perspective, with parts cut away for clarity, showing the construction of one form of deck grid,

Fig; 4 is a view in perspective showing rather diagrammatically one form of stiffening employed in conjunction with a pair of deck grids,

Fig. 5 is a View in perspective showing another form of cable and strut stiffening for deck grids,

' Fig. 6 is a'di agramm'atic view in perspective showing several deck grids coupled together and stiffened,

Fig. 7 is a view similar to Fig. 6 but showing the deck grids assembled as a catenary bridge,

' Fig. 8 is a view in perspective illustrating. the assembly of several deck grids into an arched bridge, and

Fig. 9' is a view in side elevation showing the assembly of a plurality of deck grids as a suspension bridge.

For the details of construction of one form of deck grid, or trussed craft unit, suitable for use in conjunction with the present'invention the reader is referred to mycopending application, but I have shown in Figs. 1-3 the essential elements thereof, and an inspection of these figures will show that each deck grid or trussed craft unit is composed of a tubular skeleton frame including two long side tubes 19, a central longitudinal tube 11 and shorter'end' tubes 12. The area within 2,762,069 Patented Sept. 11, 1956 the outer tubes may conveniently be covered by a grating 16 in which is included a removable manhole section 18; or the deck may be a solid sheet of Wood or steel or other suitable material. The ends of the side tubes 10 and the center tube 11 are provided with heavy hinge plates 14 which are oflset vertically and arranged in alternation so that at one end of each unit the hinge plates 14 extend downwardly, while at the opposite end they extend upwardly. Consequently a plurality of deck grids may be hinged together in series and folded in accordion fashion to form a compact stack. A stout stiffening strap 20 extends from each hinge plate casting along the top or bottom of the longitudinal tubes of the frame. Hinged to each of the side tubes 10 are heavy bars 24, the outer ends of which are secured to long tubular members 22 at the end of each of which are hinge plates 26 and which may be swung down at right angles to the deck section and secured in place by hinged struts 25 to serve as side trusses lending strength and rigidity to the deck grid.

Beneath each deck grid is a number of rows of cylindrical collapsible inflatable pontoons or bags 28, to the bottom of each of which is secured a metal shoe 30. At its upper end each bag is suitably secured to the deck in any convenient manner, as recited in my abovenamed co-pending application. The pontoons 28' collapse for storage and rest within the deck grid as shown in Fig. I, while upon inflation they extend down into the position shown in Fig. 2. I contemplate the provision of as many as 24 pontoons with each deck grid, but for the sake of clarity in the drawings I have shown each deck grid as provided only with six pontoons 28 in a manner similar to that shown in Fig. 4. The principle of operation, however, is the same, regardless of the number of pontoons. I provide means (not shown) for inflating the pontoons, the description illustrative of the inflating means being omitted here because it has been fully and entirely explained in my c'opending application above identified. Moreover, the inflating means per se forms no part of this invention as claimed. Although for many uses suflicient rigidity is incorporated into a string of deck grids by means of the side truss members 22 and their associated hinges and struts, I have devised a less cumbersome and expensive method of trussing a plurality of units as shown in Figs. 4 and 5 where vertical struts are served by longitudinally running cables; In the embodiment shown in Fig. 4 there is included a pair of deck grids 4i) and 42 (shown diagrammatically) hinged at 41, each grid being provided with sixpontoons 44. Each pontoon has at its bottom a metal shoe 46 suitably secured to the body of the pontoon and provided at each side with an eye 48. There are six. cables 45, each of which is secured at one end to the end of the deck grid and runs down beneath both of the grids 40 and 42, being secured at the far end of the adjacent deck grid. Each cable passes through two of the eyes 48 on the pontoon shoes 46, skipping. the row of pontoons nearest the far ends of the two sections 40 and .2. In Fig. 6 I have shown six deck grids, 40, 40', 40", 42, 42', and 4- It will be observed that each end of each deck grid is served by cables but that they are arranged in alternation so that each cable spans two deck grids. While the cables, as shown in the drawings, span but two grids, it is contemplated that each cable may span more than two grids, since the principle of operation is not affected by the number of grids served by each cable.

When the pontoons are collapsed, the cables 45 are slack; thus the deck sections may be folded into a stack without interference from the cables. However, when the stack is unfolded and the pontoons are inflated, the

tirely rigid "-strut members.

cables are placed under tension and the pontoons, or rather the confined air columns within them, serve as within them acting as compression members in the trussing system. An advantage of this form of stiflening is the fact that the inflated pontoons 44 are not incompressible. Consequently if an unduly heavy load is suddenly applied, the deck grids will articulate to a limited extent about the hinges and the cables will not snap. There is they further advantage that as the pontoons are compressed in response to the action of the cables under these circumstances, the resistance increases because the pres.

sure within each pontoon increases simultaneously un- 'hinges,'but the upward pressure of the flexible air-filled pontoons against the underside of the deck structure will be beneficial in counteracting such transverse sagging.

It will also be readily seen that the resistance of the cables 45 and their tr-ussing comes into play gradually with some small motionat the hinge so that the two deck grids will be heeled toward each other. This flexibility which permits the slight heeling of the deck grids thus brings into play the natural resistance of these sections to heeling, i. e. the metacentric stability of the buoyant structure. Furthermore if there are more thantwo grids,

. as shown in Fig. 6, they also will normally be heeled by the heeling of the two grids bearing the load, and these other grids will contribute further to the stability of the string. Consequently the forces which the cable and strut elements have to carry are reduced.

In Fig. there is illustrated another formof the invention in which the pontoon struts are replaced by en- In this instance there are shown two deck grids 60 and 62, with portions of adjacent grids 60' and 62 hinged thereto. The grid 60 is provided atits four corners with studs 64 on which are pivoted sturdy bars or 'struts66 in the end of each of which there is a through-and-through hole for the passage of a cable 68 running from the outer end of the grid- 60 through the upwardly extending struts 66 and to the far end of the grid 62. The grid 62 is similarly provided with pivoted strutmembers 70, two being shown in the flat storage position and two others being swung downwardly toireceive cables 74 which span the grids 60 and 62. Thus, the two grids 60 and 62 are trussed against articulation either up or down, the cable 74 serving to prevent a depression of the hinge and the cable 68 with the struts 66 serving to prevent upward articulation about the hinge joining the two grids. When it is desired to fold the grids into a stack, the struts 66 and 70 are swung parallel with the decks and the cables thus slackened sufficiently to permit folding. If desired the struts maybe pinned in either position to prevent accidental displacement thereof.

In Fig. 7 there are six hinged deck grids hung like a suspension chain between two abutments indicated 'at 50 and capable of providing the horizontal and vertical forces needed to keep the bridge deck in this suspended position when subjected to its intended live loads. The cable and strut construction is of the type shown in Figs. 4 and 6, which is adequate to insure adequate local distribution of concentrated loads so that the local bending of the deck structure at its various hinged joints is kept within limits suflicient to prevent interference, with the movement of traflic over the bridge. The action of the cable and strut elements reduces the horizontal forces applied to the abutments.

, In Fig. 8 the cable and strut construction of Fig.5

.vertical struts said pontoons and confined air columns is shown as applied to six grids assembledto form an arch bridge. The sixdeck grids are divided into units of three, each unit being provided with trussing both below and above the. deck. Furthermore there is provided a pair of tie cables 92 joining-the ends of the arch to reduce the thrust upon the abutments 80. In this form each unit consists of three grids 82 provided with upwardly extending struts 84's'erved by'cables 86 and downwardly extending struts 88 served by cables 90.

For a short span the whole length may be trussed as a single unit, just as each half is trussed in Fig. 8. V

In Fig. 9 there isshown a suspension bridge formed from three units of the type-shown in Figs. 1-3, 'This bridge includes a pair of cable anchors which serve one of the two main suspension cables 102, each of which runs to a pair ofposts 104 mounted in position on the opposite ends of the bridge.- The bridge is composed of three deck grids 10 hinged at 14 and provided with side truss members 22 hinged together as shown diagrammatically at 26. Suspender cables 112 connect the main suspension cable 102 with the bridgedeck at the hinge points, 14. Although the suspension bridge has been shown'as constructed of deck grids with the rigid side truss elements as shown in Fig. 2, such a bridge may be constructed with equal facility from deck grids provided with the strut and cable stiffening shown in Fig. "4 or S.

In any application .of the cable and strut stiflening to folding bridge decks, the deck structure may either'be floated into place or transported by rail, overhead cables, or the like. If it is tobe floated into position, the necessary buoyancy is provided in the grids themselves, the tubular frames thereof, or by pontoons or auxiliary floats. This is also true when the structure is used as a barge, lighter, floating or beached. causeway, dry dock, or-other waterborne device;

It will be evident that if the eflective length of the outboard edge of each'side truss panel, of the type shown 'at 22 in Fig. 2, is the same as the eflective length of the deck grid to which it is attached, the deck will be stiflened in a straight or plane form, but if the outboard edge of the truss is longer or shorter than the eflective length of the deck grid to which it is connected, the latter will not lie in a plane but will approximate a curvedsurface, the surface curving one way or the other depending upon 7 whether the effectiveilength of the truss is shorter or longer than that of the deckgrid. This fact may 'betaken into account in constructing arched and catenary' forms of deck bridges as shown in Figs. 7 and 8.

Although in Figs. 6 and 7 to promote clarity :of presentation only one row of pontoons has been illustrated,

it is to be understood that the arrangement is" to be the sameas that shown in Fig. 4; Obviously the exact; number of pontoons to be employed will be dictated by the application intended for the appliance. As indicated above, the use of as many as24 pontoons with each'grid is contemplated.

Moreover, although the structure illustrated in Fig. '9' does not carry pontoons, itmay prove desirable to em! ploy pontoons if the structure must be floated to thepar ticularsite of use. After the structu'reis secured inposh tion, the pontoons may be removed or collapsed and retained in place to reduce wind loadings. The latter is particularly desirable if the .bridge is to be later moved to another site. i

Having now,described and illustrated .a ,preferredemeach cable being secured to one end of one of said deckgrids, engaging a plurality ot-said inflatable members under at least two deck grids and being securedat-its other end to the end of another deck grid, whereby; inflationof said member will tension said} cables. 1;; p

2. A trussed structure comprising a plurality of deck grids hinged in series, a plurality of rows of inflatable members disposed beneath each of said deck grids, a shoe secured to the bottom of each of said members, and cables secured to the far ends of adjacent grids and engaging the shoes on at least one of said inflatable members under each grid.

3. A trussed structure comprising a plurality of deck grids, fastening means fixed to the ends of each of said grids for joining said grids in series relationship, cables spanning two grids and secured at their ends to said grids adjacent said fastening means, and collapsible compression members projecting from said grids and engaging said cables.

4. A trussed structure comprising a plurality of buoyant deck grids, fastening means fixed to the ends of each of said grids for joining said grids in series relationship, cables spanning two grids and secured at their ends to said grids adjacent said fastening means, and collapsible compression members projecting from said grids and engaging said cables.

5. A trussed structure comprising a plurality of deck grids, fastening means fixed to the ends of each of said grids for joining said grids in series relationship, a plurality of inflatable collapsible pontoons disposed beneath each grid, and a cable spanning at least two of said grids, secured to alternate ends of adjacent grids adjacent said fastening means and engaging said pontoons.

6. A bridge comprising a plurality of deck grids hinged in series, a first cable spanning the entire series and connected to the end of the series, said cable being shorter than said series, pivotally mounted strut members secured to each of said grids movable to a substantially vertical position, and a plurality of cables spanning at 6 least two of said grids secured to alternate ends of adjacent grids and engaging said strut members to stifien said grids in arched position.

7. A trussed structure comprising a plurality of deck grids hinged in series, a plurality of cables secured at each end to and running longitudinally along said grids beneath said series of grids, and inflatable collapsible members secured to said grids and to said cables intermediate the ends of said cables, said members being inflated to tension said cables.

8. A trussed structure comprising a plurality of deck grids hinged in series, a plurality of cables spanning two adjacent grids and running longitudinally along said series, and movable struts secured to said grids and to said cables positioned to tension said cables and being adapted to be moved to a position to permit relative pivotal movement of said grids.

References Cited in the file of this patent UNITED STATES PATENTS 41,719 Perry Feb. 23, 1864 511,472 Sumovski Dec. 26, 1893 1,115,775 Bisbach Nov. 3, 1914 1,415,554 Hatch May 9, 1922 1,640,980 Caroni Aug. 30, 1927 1,788,264 Wilson Jan. 6, 1931 1,973,584 Tatter et a1. Sept. 11, 1934 2,480,144 Laycock Aug. 30, 1949 FOREIGN PATENTS 4,093 Great Britain Feb. 28, 1884 4,224 Great Britain Feb. 23, 1903 264,872 Germany Sept. 29, 1913 65,502 Austria Jan.. 15, 1914 

